Inhaler

ABSTRACT

An inhaler for delivery by inhalation of a medicament from the canister which is compressible to deliver a dose of medicament. The inhaler comprises a housing ( 1 ) for holding a canister ( 2 ) having a generally cylindrical body ( 3 ) with the cylindrical axis of the body ( 3 ) in predetermined direction and a loading mechanism for loading a resilient loading element ( 7 ) which is arranged, when loaded, to bias compression of the canister ( 2 ). The loading mechanism comprises a loading member ( 8 ) engaging the resilient loading element ( 7 ) and two contact members ( 9 ) movable relative to the housing ( 1 ) in a movement direction orthogonal to said predetermined direction and arranged to drive the loading member ( 8 ) to load the resilient loading element ( 7 ), through a cam arrangement between the contact member ( 8 ). The cam arrangement may allow for the ratio of the amount of driven movement of the loading member ( 8 ) to the amount of mount of the contact members ( 9 ) to be non-linear, preferably reducing over the driven movement to compensate for the increasing resistance by the resilient loading element.

[0001] The present application relates to an inhaler for delivery ofmedicament from a canister, particularly to an actuation mechanism foractuating a canister held in the inhaler.

[0002] Inhalers are commonly used to deliver a wide range ofmedicaments. The inhaler holds a canister of medicament which isactuatable, for example by compression, to deliver a dose of medicament.Some known inhalers are provided with an actuation mechanism foractuating the canister. The mechanism may be breath-actuated ie.arranged to actuate the canister in response to inhalation at the mouthpiece. Typically a breath-actuated inhaler includes a loading mechanismfor loading a resilient loading element with an actuation force forcompression of the canister. A triggering mechanism may be provided tohold the resilient loading element against compression of the canister,the triggering mechanism releasing the resilient loading element uponinhalation.

[0003] Important considerations for an actuation mechanism arereliability and simplicity. Reliability is important to ensure that themedicament is correctly delivered on every use, especially when themedicament is required by the user in an emergency. A simple structureis required firstly to assist in ensuring that the actuation mechanismoperates reliably and secondly to simplify manufacture, thereby reducingmanufacturing costs.

[0004] A problem often encountered, especially by elderly, young andinfirm users, is that it is difficult to generate enough force to loadthe resilient loading element provided to bias actuation of thecanister. The energy with which the resilient loading element is loadedmust be sufficient to actuate the canister which can create difficultiesfor some users. The first aspect of the present invention is intended toassist in loading of the mechanism.

[0005] According to the first aspect of the present invention, there isprovided an inhaler for delivery by inhalation of a medicament from acanister which is compressible to deliver a dose of medicament, theinhaler comprising a housing for holding a canister having a generallycylindrical body with the cylindrical axis of the body in predetermineddirection;

[0006] a loading mechanism for loading a resilient loading element whichis arranged, when loaded, to bias compression of the canister, theloading mechanism comprising:

[0007] a loading member engaging the resilient loading element; and

[0008] at least one contact member movable relative to the housing in amovement direction orthogonal to said predetermined direction andarranged to drive the loading member to load the resilient loadingelement through a cam arrangement between the at least one contactmember and the loading member.

[0009] By arranging the contact member(s) to be movable relative to thehousing in a movement direction orthogonal to the cylindrical axis ofthe body of the canister held in the housing, loading is made easier.The inhaler may be held in the palm of one hand with the body of thecanister aligned generally upwardly. Sideways movement of the contactmember(s) may then be easily achieved by gripping the inhaler between afinger and thumb. A cam arrangement is particularly advantageous fordriving the loading member to load the resilient loading element througha cam arrangement between the contact member(s) and the loading member.It meets the requirements for both reliability and simplicity.Furthermore it allows the loading member to be suitably arranged in theinhaler when the contact member(s) have the convenient arrangement ofbeing movable orthogonal to the predetermined direction of the axis ofthe canister.

[0010] In particular, the cam arrangement allows the movement of thecontact member(s) to be converted into movement of the loading member ina direction orthogonal to said movement direction, ie. in a planeparallel to the predetermined direction in which the cylindrical axis ofthe body of the canister is held. As a result, the resilient loadingelement may be simply configured to bias compression of the canister.

[0011] Desirably the loading member is driven to rotate in saiddirection orthogonal to said movement direction. This is advantageousbecause it converts the linear force provided to the contact member(s)into a rotational movement. This assists in loading of the resilientloading element and provides a simpler and more reliable mechanism thanif the loading element was movable linearly, say along a track.

[0012] The resilient loading element may be a torsion spring. It maybias a canister engagement member engageable with a canister held in thehousing to compress the canister which may be a lever rotatable about anaxis parallel to the movement direction of the at least one contactmember. Thus, a simple configuration with a reliable action is provided.

[0013] Preferably, the inhaler has two contact members disposed onopposite sides of the housing. This improves the ease of operation. Thetwo contact members may be depressed together between a finger and athumb with the inhaler held in the palm of a hand. An alternative wouldbe to provide a single contact member which the user may push relativeto the housing.

[0014] According to a second aspect of the present invention an inhalerfor delivery by inhalation of a medicament from a canister which iscompressible to deliver a dose of medicament, the inhaler comprising:

[0015] a housing for holding a canister;

[0016] a loading mechanism for loading a resilient loading element whichis arranged, when loaded, to bias compression of the canister, theloading mechanism comprising:

[0017] a loading member engaging the resilient loading element; and

[0018] at least one contact member movable relative to the housing todrive the loading member to load the resilient loading element, theratio of the amount of driven movement of the loading member to theamount of movement of the at least one contact member being a non-linearfunction of the position of the loading member.

[0019] As a result of the gearing ratio of the amount of driven movementof the loading member to the amount of movement of the contact member(s)being a non-linear function of the position of the loading member, it ispossible to control the amount of force which the user needs to applyover the movement stroke of the contact member(s) relative to thehousing. This technique can be used to produce a number of technicaladvantages.

[0020] Preferably, said ratio reduces during at least a major portion ofthe driven movement of the loading member. This allows compensation forthe reactive force generated by the resilient biassing element whichmust be overcome by the user. Generally, this reactive force increasesas the resilient loading element is loaded. However compensation isprovided by ensuring that the gearing ratio reduces during the drivenmovement of the loading member which in itself reduces the amount offorce required by the user.

[0021] Desirably, the ratio varies such that the necessary force appliedto the at least one contact member is substantially constant. If theloading force of the resilient biassing element increases linearly (byan amount which is for example proportional to the spring constant ifthe resilient loading element is a spring), then a linear resistance maybe achieved if the ratio is inversely proportional to the position ofthe loading member during said major portion of its driven movement.

[0022] Secondly, varying the ratio non-linearly with the position of theloading member can provide the inhaler with a particular feel to theuser operating the contact members. For example, it is desirable thatwherein said ratio is reduced during an initial portion of the drivenmovement of the loading member relative to the subsequent portion. Inthis way, the user initially feels a relatively low resistance tomovement of the contact members. This not only increases the quality ofthe inhaler as perceived by the user, but also assists in application offorce.

[0023] The second aspect of the present invention may be implemented bymeans of the contact member(s) driving the loading member through anon-linear cam arrangement for example with an inhaler according to thefirst aspect of the present invention. In fact, the first and secondaspects of the present invention may be embodied by the same actuationmechanism and features associated with each aspect may be freelycombined to advantage.

[0024] The first and second aspects of the present invention areparticularly suitable for use in an inhaler arranged to hold theresilient loading element against actuation of the canister andtriggerable to release the resilient loading element or abreath-actuated inhaler in which the triggering mechanism is arranged tobe triggered by inhalation.

[0025] To allow better understanding, an inhaler which embodies thepresent invention will now be described by way of non-limitative examplewith reference to the accompanying drawings, in which:

[0026]FIG. 1 is a side view of the inhaler;

[0027]FIG. 2 is a cross-sectional view of the inhaler illustrating thehousing and duct;

[0028]FIG. 3 is a side view of the duct;

[0029]FIG. 4 is a side view of the canister and duct assembled together;

[0030]FIG. 5 is an exploded view of the canister, collar and duct;

[0031]FIG. 6 is a cross-sectional view of the canister and dustassembled together;

[0032]FIG. 7 is a view from the side and rear of the actuationmechanism;

[0033]FIG. 8 is a view from the rear of the spindle;

[0034]FIG. 9 is a view from the side, rear and above showing thearrangement of the resilient loading element;

[0035]FIG. 10 is a schematic view of the cam surfaces formed on thespindle;

[0036]FIG. 11 is a view from the side and rear of the triggeringmechanism;

[0037]FIG. 12 is a side view of the triggering mechanism;

[0038]FIG. 13 is a side view of the locking mechanism;

[0039]FIGS. 14A to 14F are graphs showing the angular positions of theelements of the actuation mechanism during its operation sequence; and

[0040] FIGS. 15 to 22 are views of the actuation mechanism in variousstates during its operation sequence with views from opposite sidesbeing suffixed by the letters A, B respectively.

[0041] As illustrated in FIG. 1, the inhaler has a housing 1 comprisingan upper portion 19 and a lower portion 20. As illustrated in thecross-sectional view of FIG. 2, the upper housing portion 19 is a hollowshell which holds a canister 2 of medicament having a generallycylindrical body 3 held with its axis in a predetermined direction,vertical in FIG. 2. The upper housing portion 19 houses an actuationmechanism for actuating the canister 2 which will be described in moredetail below.

[0042] The interior of the upper housing portion 19 is open to theatmosphere by means of air inlets 51 formed in the upper wall 52 of theupper housing portion 19. The location of the air inlets 51 minimisesocclusion by the users hand which will normally grip the sides of thehousing 1 and not cover the upper wall 52.

[0043] The canister 2 is compressible to deliver a dose of medicament.In particular the canister 2 has a valve stem 4 which is compressiblerelative to the body 3 to deliver a dose of medicament from the valvestem 4. The canister is of a known type including a metering chamberwhich captures a defined volume the medicament from the body 3 of thecanister 2. This volume of medicament is delivered as a metered dosefrom the valve stem 4 on compression of the valve stem 4 relative to thebody 3. The valve stem 4 is weakly biassed outwardly by an internalvalve spring (not shown) to reset the canister 2 after compression forrefilling the metering chamber.

[0044] The lower housing portion 20 is a hollow shell connected to theupper housing portion 19 by a sliding joint (not shown) which allows thelower portion 20 to be separated in the direction of the arrow in FIG. 1by the user gripping textured surfaces 21 formed on the upper and lowerhousing portions 19 and 20. A cap 22 is hinged to the lower housingportion 20 by a flexible joint 23 to cover and uncover a mouthpiece 5protruding from the lower housing portion 20.

[0045] As shown in FIG. 2, the lower housing portion 20 houses a duct 24which is integrally formed with the mouthpiece 5, as illustrated inisolation in FIG. 3.

[0046] The duct 24 is assembled with a canister 2 as shown in FIGS. 4 to6. The duct 24 receives a nozzle block 11 in an opening 25. The valvestem 4 of the canister is received in the nozzle block 11 which isarranged to direct a dose of medicament delivered from the valve stem 4out of the inhaler through the mouthpiece 5. The duct 24 and nozzleblock 11 are separately formed. This allows each to be manufactured andsubsequently assembled. This produces manufacturing and logisticalsavings because it facilitates different nozzle block designs beingincorporated with a single duct design and vice versa.

[0047] A collar 26 is permanently connected to the canister 2. Thecollar 26 includes an annular retaining ring 27 permanently fittedaround a necked portion 28 of the canister body 3. The retaining portion27 prevents removal of the collar 26 from the canister such that thecollar 26 is removed and replaced together with the canister 2. However,the retaining portion 27 and the canister 2 have a small degree ofrelative movement along the axis of the canister 5 to allow compressionof the canister body 2 towards the valve stem 4.

[0048] The collar 26 further includes a front panel 29 integrally formedwith the retaining ring 27. When the canister 2 is inserted in thehousing 1, the front panel 29 of the collar 26 closes an opening formedbetween the upper housing portion 19 and the lower portion 20 andtherefore forms a part of the outer wall of the housing 1. Accordingly,the presence or absence of the front panel 29 provides a visualindication to the user of whether or not a canister 2 has been insertedin the canister, because the collar 26 is permanently connected to thecanister 2.

[0049] A pair of catch arms 30 integrally formed with the front panel 29of the sides of the collar 26 catch the interior surface of the upperhousing portion 19 to hold the collar 26 and the canister 2 in the upperhousing portion 19.

[0050] The lower housing portion 20 has a stud 50 which locates the endof the nozzle block 11 as shown in FIG. 2 to hold the lower housingportion 20 and the duct 24 in place relative to one another. However,the lower housing portion 20 is not retained on the duct 24, so may beremoved from the upper housing portion 19 leaving the canister 2inserted in the upper housing portion 19 and the duct 24 held on thecanister 2 by the valve stem 4 being inserted in the nozzle block 11.The duct 24 and nozzle block 11 may subsequently be slid off the valvestem 4 for cleaning or replacement. The canister 2 and collar 26 may beslid out from the upper housing portion 19 after depression of the catcharms 30. Subsequently a replacement canister 2 and collar 26 may beinserted.

[0051] Typically a new duct 24 and nozzle block 11 will be provided tothe user with each new canister 2 so that the duct 24 and mouthpiece 5are regularly replaced to prevent damage or dirt building up over time.The duct 24 has an opening 31 at its end opposite from the mouthpiece 5.

[0052] As shown in FIG. 2, the upper housing portion 19 holds a flapduct 32 which extends from a flow inlet 33 to a flap 13 which forms partof the triggering mechanism for the actuation mechanism as described indetail below. Therefore the duct 24 housed in the lower housing portion19 and the flap duct 32 together define a composite duct shaped todirect the inhalation flow from the mouthpiece 5 to the flap 13. Thecomposite duct formed by the duct 24 and the flap duct 32 is shaped tocontrol the flow to the flap 13 to provide appropriate flowcharacteristics for proper operation of the flap 13.

[0053] The inhaler is further provided with an actuation mechanism 6. Toassist understanding, a general description of the overall structure andoperation of the actuation mechanism 6 will first be given.

[0054] An actuation force for compressing the canister 2 is stored in aresilient loading element in the form of a torsion spring 7. To load thetorsion spring 7, the actuation mechanism 6 includes a loading mechanismconsisting of a loading member in the form of a rotatable spindle 8 andtwo contact members in the form of buttons 9 which protrude from thehousing as shown in FIG. 1. Depression of the buttons 9 towards oneanother, relative to the housing 1, drives the loading member 8 to loadthe torsion spring 7 through a cam arrangement between the buttons 9 andspindle 8.

[0055] The torsion spring 7 biasses compression of the canister 2 byengaging a canister engagement member in the form of a lever 10 whichdepresses the body 3 of the canister towards the stem 4 held in thenozzle block 11.

[0056] To allow storage of the actuation force in the torsion spring 7after loading, the actuation mechanism 6 includes a triggeringmechanism. This includes a locking lever 12 which holds the canisterengagement lever 10 against compression of the canister 2. To releasethe canister engagement lever 10, the triggering mechanism furtherincludes a vane in the form of a flap 13 which in a rest state holds thelocking lever 12 in place. Inhalation at the mouthpiece 5 moves the flap13 to release the locking member 12. This in turn releases the canisterengagement lever 10 allowing the torsion spring 7 to drive compressionof the canister 2.

[0057] The actuation mechanism 6 further includes a locking mechanismwhich locks the spindle 8 after loading of the torsion spring 7, therebyholding the torsion spring 7 in its loaded state before triggering andlocking the canister in its compressed state after triggering.

[0058] The locking mechanism includes a catch 14 which, in a lockingposition, catches the spindle 8 and holds the torsion spring 7 in itsloaded state. The locking mechanism further includes an intermediatemember 15. A resilient biassing element in the form of a spring 16 isprovided between the catch 14 and the intermediate member 15 to bias thecatch 14 towards its locking position. The spring 16 allows deflectionof the catch 14 by the spindle 8 during loading of the torsion spring 7.

[0059] Prior to inhalation the intermediate member 15 is held in placeby the canister engagement lever 10. Upon inhalation at the mouthpiece5, the flap 13 engages the intermediate member 15 to hold it in place.After compression by the canister engagement lever 10, the canister 2 islocked in its compressed state by the catch 14 of the locking mechanismholding the spindle 8 in place.

[0060] When the level of inhalation at the mouthpiece falls below apredetermined threshold, the flap 13 releases the intermediate member 15to unload the biassing element 16 which in turn allows the catch 14 torelease the spindle 8. After release by the catch 14, the spindle 8,torsion spring 7 and canister engagement lever 10 move upwardly and thecanister resets.

[0061] Now there will be given a detailed description of the actuationmechanism 6, the entirety of which is illustrated in FIG. 7 and parts ofwhich are illustrated in FIGS. 8 to 13.

[0062] The loading mechanism is illustrated in FIG. 8 and consists of arotatable spindle 8 and two contact members in the forms of buttons 9 atboth ends. The spindle 8 is rotatably mounted in the upper housingportion 19 about an axis orthogonal to the axis of the cylindrical body3 of the canister 2. The spindle 8 has a pair of cam surfaces 8 adisposed on opposite sides of the rotational axis of the spindle 8. Thebuttons 9 are mounted in the housing to be movable in a movementdirection parallel to the rotational axis of the spindle 8. The buttons9 each have a pair of inwardly projecting cam followers 9 a which eachengage a respective cam surface 8 a of the spindle 8. The camarrangement of the cam surfaces 8 a and the cam followers 9 a betweenthe spindle 8 and the buttons 9 causes depression of the buttons 9 todrive rotation of the spindle 8.

[0063] As illustrated in FIG. 9, the torsion spring 7 which forms theresilient loading element is disposed with its coils 7 a encircling acentral cylindrical surface 8 b of the spindle 8. A catch arm 8 cprotrudes radially from the spindle 8. A first leg 7 b of the torsionspring 7 is restrained by the catch arm 8 c so that the movement of thespindle 8 driven by the buttons 9 loads the torsion spring 7.

[0064] As illustrated schematically in FIG. 10, the cam surfaces 8 ahave a non-linear shape which causes the gearing ratio of the amount ofdriven movement of the spindle 8 to the amount of movement of thebuttons 9 to be a non-linear function of the rotational position of thespindle 8. The major portion 8 b of each cam surface 8 a is shaped withincreasing pitch to compensate for the increased reactive loading forceapplied by the torsion spring 7 to the spindle 8 as the buttons 9 aredepressed. In particular, they are shaped such that the necessary forceapplied to the buttons is substantially constant so the user feels alinear resistance. As the torsion spring 7 has a linear spring constant,this is achieved by shaping the major portion 8 b of each cam surface 8a such that the gearing ratio is inversely proportion to the rotationalposition of the spindle 8.

[0065] Optionally, the outermost portion of the cam surfaces 8 a whichare contacted by the cam followers 9 a during the initial portion of thedriven movement of the spindle may have a decreased pitch, for exampleas illustrated by the dotted lines 8 e. This is to reduce the gearingratio relative to the subsequent major portion 8 b. In this way the userinitially feels a low resistance to movement of the buttons 9. Thisimproves the feel perceived by the user and also assists the user inapplying force.

[0066] Another option is to provide the final portion of the cam surface8 a with a detent, for example as illustrated by the dotted lines 8 d.When the end of the cam followers 9 a reach the detent 8 d, the camsurface 8 a of the spindle 8 no longer exerts a force urging the buttonsoutwardly on the buttons 9. At this position the detent 8 d is urged bythe torsion spring 7 against the side of the cam followers 9 a andtherefore holds the buttons 9 in their innermost position. This preventsthe buttons 9 from loosely sliding back and forth after the torsionspring 7 has been loaded.

[0067] As shown in FIG. 9, the torsion spring 7 engages a canisterengagement lever 10 which is pivotally mounted to the interior of thehousing about an axis 10 a. The canister engagement lever 10 isgenerally U-shaped with two parallel sides 10 b by a cross piece 10 c. Abar 10 d extending between the two sides 10 b bears on the body 5 of thecanister 2. A mount 10 e formed on the cross-piece 10 c is engaged bythe second leg 7 c of the torsion spring 7, whereby loading of thetorsion spring 7 biasses the lever 10 to compress the canister 2. Thecanister engagement lever 10 is biassed upwardly by a reset spring (notshown), which may be arranged as a torsion spring on the axis 10 a, butthis is weaker than the torsion spring 7.

[0068] The torsion spring 7, spindle 8 and canister engagement lever 10are all rotatable about axis orthogonal to the cylindrical axis of thebody 5 of the canister 2. This provides a simple and reliable loadingmechanism particularly because of the arrangement of the torsion spring7 with its coils 7 a encircling the spindle 8. Some or all of theseelements could alternatively be linearly movable in a plane parallel tothe cylindrical axis of the body 5 of the canister 2 to achieve aloading mechanism which is equally simple to construct. Howeverrotatable elements are preferred from the point of view of reliabilityin repeated use of the actuation mechanism 6.

[0069] On the other hand, the movement of the buttons in a directionorthogonal to the cylinder axis of the body 3 of the canister 2 assiststhe user in application of force to the loading mechanism. As typicalfor inhalers, the housing 1 extends in the direction of the cylindricalaxis of the body 3 of the canister 2, so may be easily held in the palmof a hand with the buttons 9 protruding from either side. Thus thebuttons 9 are easily depressed between a finger and thumb. Alternativelya single button could be provided allowing loading in a similar mannerby the user pressing the button and the housing on the opposite side tothe button. Either configuration also allows loading by laying theinhaler on a surface and applying force for example with the palm of ahand. This facilitates loading by a user with limited finger control ormovement, for example a chronic arthritis sufferer.

[0070] The actuation member mechanism 6 includes a triggering mechanismas illustrated in FIGS. 11 and 12 which allows storage of the actuationforce in the torsion spring 7 after loading.

[0071] The triggering mechanism includes a locking lever 12 which ispivotably mounted on an axle 17 extending across the interior of thehousing 1. The locking lever 12 has a notch 12 a adjacent the axle 17.In a reset state shown in FIG. 12, the notch 12 a holds a protrusion 10f protruding from the cross-piece 10 c of the canister engagement lever10, thereby holding the lever 10 against compression of the canister 2.The locking lever 12 is weakly biassed towards the position shown inFIGS. 11 and 12 by a reset spring 34 arranged as a torsion spring on theaxle 17.

[0072] The triggering mechanism further includes a vane in the form of aflap 13 which is rotatably mounted on an axle 18 extending across theinterior of the housing 1. The flap 13 biassed by a reset spring (notshown), which may be arranged as a torsion spring on the axle 18,towards the position shown in FIG. 12. The flap 13 has a locking leverengagement surface 13 a which protrudes from a block 13 b positionedabove the axle 18. In the position shown in FIG. 12, the engagementsurface 13 a engages a contact surface 12 b formed on the end of thelocking lever 12 distal from the axle 17 to hold the locking lever 12 inplace holding the canister engagement lever 10.

[0073] The flap 13 is disposed in the composite duct formed by the duct24 and the flap duct 32 extending from the mouthpiece 5 with a flapportion 13 c extending across the composite duct at the opposite endfrom the mouthpiece 5, where the duct opens into the interior of thehousing 1. Therefore, the flap 13 is responsive to inhalation at themouthpiece 5.

[0074] Inhalation of the mouthpiece draws the flap portion 13 c into theflap duct 32 (clockwise in FIG. 2 and anticlockwise in FIG. 12). Suchrotation of the flap 13 allows the locking lever engagement surface 13 ato move out of contact with the contact surface 12 b of the lockinglever 12.

[0075] The upper housing portion 19 also mounts a button 35 disposedadjacent the flap 13 above the axle 18 so that depression of the button35 rotates the flap 13 in the same direction as inhalation at themouthpiece 5. Therefore, the button 35 allows the actuation mechanism 6to be manually released without inhalation at the mouthpiece 5, forexample to allow actuation of the canister 2 for testing.

[0076] When the canister engagement lever 10 is loaded by the torsionspring 7, release of the locking lever 12 by the flap 13 allows thecanister engagement lever 10 to be driven to compress the canister 2.The protrusion 10 f deflects the locking lever 12 (anticlockwise in FIG.12) as the canister engagement lever 10 passes.

[0077] As illustrated in FIG. 13, the actuation mechanism 6 furtherincludes a locking mechanism for locking the spindle 8 after loading ofthe torsion spring 7. The locking mechanism comprises a catch 14 and anintermediate member 15 which are both pivotally mounted on the axle 17,adjacent the locking lever 12. Before compression of the canister 2, theintermediate member 15 is held in the position illustrated in FIG. 13 bythe cross-piece 10 c of the canister engagement lever 10 contacting afirst contact surface 15 a adjacent the axle 17. A resilient biassingelement in the form of a torsion spring 16 is connected between thecatch 14 and the intermediate member 15 and loaded to bias the catch 14towards its locking position shown in FIG. 13.

[0078] The catch 14 has a notch 14 a adjacent the axle 17 for engagingthe arm 8 c of the spindle 8 after rotation to the position illustratedin FIG. 13 where the torsion spring 7 is loaded. In this position, theloading provided by the spring 16 prevents release of the spindle 8 andthereby holds the torsion spring 7 in its loaded state. Before loading,the arm 8 c of the spindle 8 is positioned above the end 14 b of thecatch 14 distal from the axle 17. When the spindle 8 is driven downwardsby depression of the buttons 9, the arm 8 c of the spindle engages theend 14 b of the catch 14 and deflects the catch 14 by compressing thespring 16 to allow passage of the arm 8 c of the spindle 8.

[0079] The flap 13 further includes a stud 13 d protruding from theblock 13 b on the opposite side of the axle 18 from the locking leverengagement surface 13 a. Upon inhalation at the mouthpiece 5, the flap13 moves to the position illustrated in FIG. 13 where the stud 13 dengages a second contact surface 15 b of the intermediate member 15distal from the axle 17. Prior to this point, the stud 13 d does notcontact the second contact surface 15 b but the intermediate member 15has been held in place by the canister engagement lever 10. Movement ofthe flap 13 triggers the triggering mechanism to release the canisterengagement member 10 which moves downwards out of contact with theintermediate member 15. However, the stud 13 d catches the contactsurface 15 b and so continues to hold the intermediate member 15 withthe spring 16 loaded. Accordingly, the catch 14 remains in its lockingposition locking the spindle 8 by engagement of the arm 8 c of thespindle 8 in the notch 14 a of the catch 14.

[0080] Subsequently, when the level of inhalation of the mouthpiecefalls below a predetermined threshold, the flap moves out of contactwith the intermediate member 15 (clockwise in FIG. 13). The level of thepredetermined threshold at which the flap 13 releases the intermediatemember 15 is controlled by the shape of the second contact surface 15 bof the intermediate member 15.

[0081] After release by the flap 13, the intermediate member 15 isdriven by spring 16 which unloads (clockwise in FIG. 13). Such unloadingof the spring 16 reduces the force by which the catch 14 is biassedtowards its locking position. Accordingly, the force of the torsionspring 7 acting on the canister engagement lever 10 is sufficient toforce the catch arm 8 c of the spindle 8 out of the notch 14 a.Accordingly, the spindle 8, the torsion spring 7 and canister engagementlever 10 are able to move upwardly biassed by the reset spring acting onthe canister engagement lever 10, thereby allowing the canister toreset.

[0082] The sequence of operation of the actuation mechanism 6 will nowbe described with reference to FIGS. 14 to 22. FIGS. 14A to 14F aregraphs showing the angular positions of the various elements of theactuation mechanism 6. In particular, FIG. 14A illustrates the angularposition of the flap 13; FIG. 14B illustrates the angular position ofthe locking lever 12; FIG. 14C illustrates the angular position of thecanister engagement lever 10; FIG. 14D illustrates the angular positionof the intermediate member 15; FIG. 14E illustrates the angular positionof the catch 14; and FIG. 14F illustrates the angular position of thespindle 8. Various states and positions of the actuation mechanism 6 arelabelled by the letters A to R in FIGS. 14 and FIGS. 15 to 22 illustratethe actuation mechanism 6 in some of these states with the views fromopposite sides being suffixed by the letters A and B, respectively.

[0083] The sequence commences in state A as shown in FIG. 15 in whichthe torsion spring 7 has been loaded by depression of the buttons 9 andthe spindle 8 is locked by the catch 14. In state A, the canisterengagement lever is 10 held by the locking lever 12. The inhaler may bestored with the actuation mechanism 6 in state A.

[0084] At position B, the user starts to inhale. The flap 13, beingresponsive to such inhalation, starts to move. The shape of the contactsurface 12 b allows the locking lever 12 to start moving slowly. Theactuation mechanism 6 is now in state C illustrated in FIG. 16.

[0085] At position D, the locking lever engagement surface 13 a of theflap 13 releases the contact surface 12 b of the locking lever 12.Accordingly, the canister engagement member 10 under the loading of thetorsion spring 7 starts to rotate downwards deflecting the locking lever12 against its reset spring as the projection 10 f moves out of thenotch 12 a. The actuation mechanism is now in state E illustrated inFIG. 17.

[0086] At position F, the canister engagement lever 10 moves out ofcontact with the first contact surface 15 a at the intermediate member15 which therefore starts to move under the biassing of spring 16.However, the intermediate member 15 only moves a short way because atposition G it is caught by the flap 13, in particular by the bar 13 d ofthe flap 13 contacting the second contact surface 15 b. This contactstops the movement of the flap 13 and the intermediate member 15.

[0087] The movement of the canister engagement lever 10 compresses thebody 3 of the canister 2 relative to the stem 4 held in the nozzle block11, thereby causing the canister 2 to deliver a dose of medicament. Thenozzle block 11 directs the dose of medicament out of the mouthpiece atwhich the user is inhaling. The actuation mechanism 6 is now in state Hillustrated in FIG. 18.

[0088] When the level of inhalation starts to fall, at position I theflap 13 under the biassing of its reset spring starts to move backclosing the duct. This movement of the flap 13 causes the intermediatemember 15 to move slightly due to the shape of the second contactsurface 15 b.

[0089] When the level of inhalation falls below the predeterminedthreshold, at position J the bar 13 d of the flap 13 moves out ofcontact with the second contact surface 15 b. This releases theintermediate member 15. Under the action of the spring 16, theintermediate member 15 moves to unload the spring 16. The actuationmechanism 6 is now in state K illustrated in FIG. 19.

[0090] At position L the load on the catch 14 from the spring 16 reducesto the extent that the catch 15 can no longer hold the spindle 8. Theforce of the torsion spring 7 forces the arm 8 c of the spindle 8upwards and out of engagement with the notch 14 a of the catch 14. Thisforces the catch 14 backwards. The actuation mechanism 6 is now in stateM illustrated in FIG. 20.

[0091] At position N, the torsion spring 7 reaches its neutral, unloadedposition, so there is no load between the canister engagement lever 10and the spindle 8. Thereafter the canister engagement lever 10 and thetorsion spring 8 are moved under the action of the reset spring biassingthe canister engagement lever 10.

[0092] At position O, the canister engagement lever 10 contacts thefirst contact surface 15 a of the intermediate member 15 and forces itbackwards. The actuation mechanism is now in state P illustrated in FIG.21. This loads the spring 16 and pushes the catch 14 towards its lockingposition until the catch 14 contacts the arm 8 c of the spindle 8 whichhas now passed out of the notch 14 a.

[0093] At position Q, the projection 10 f of the canister engagementlever 10 moves into the notch 12 a of the locking lever 12 which snapsback into its locking position under the action of its reset spring. Theactuation mechanism 6 is now in state R in FIG. 22. In state R, thecanister is reset and ready to be compressed again for delivery of thenext dose, but the actuation mechanism 6 is relaxed with the torsionspring 7 unloaded. The rotation of the spindle 8 has forced the buttons9 outwards to the position illustrated in FIG. 22. The actuationmechanism 6 is ready to be loaded once again by compression of thebuttons 9. The user is instructed to do this immediately afterinhalation, so that the canister may be stored in a state ready to beused simply by inhaling at the mouthpiece 5.

[0094] When the user depresses the buttons 9 at position S, this drivesthe spindle 8 downwards. The arm 8 c of the spindle 8 deflects the catch14 slightly against the loaded spring 16 until the arm 8 c moves intothe notch 14 a. This allows the spring 16 to snap the catch 14 into itslocking position.

1. An inhaler for delivery by inhalation of a medicament from a canisterwhich is compressible to deliver a dose of medicament, the inhalercomprising a housing for holding a canister having a generallycylindrical body with the cylindrical axis of the body in predetermineddirection; a loading mechanism for loading a resilient loading elementwhich is arranged, when loaded, to bias compression of the canister, theloading mechanism comprising: a loading member engaging the resilientloading element; and at least one contact member movable relative to thehousing in a movement direction orthogonal to said predetermineddirection and arranged to drive the loading member to load the resilientloading element through a cam arrangement between the at least onecontact member and the loading member.
 2. An inhaler according to claim1, having two contact members disposed on opposite sides of the housing.3. An inhaler according to claim 1 or 2, wherein the cam arrangementincludes at least one cam surface provided on the loading member andengaged by the at least one contact member.
 4. An inhaler according toany one of the preceding claims, wherein the loading member is driven tomove in a direction orthogonal to said movement direction.
 5. An inhaleraccording to claim 4, wherein the loading member is driven to rotate insaid direction orthogonal to said movement direction.
 6. An inhaleraccording to claim 5, wherein the resilient loading element is a torsionspring.
 7. An inhaler according to claim 6, wherein the coils of thetorsion spring encircle the spindle.
 8. An inhaler according to any oneof the preceding claims, wherein the resilient loading element biases acanister engagement member engageable with a canister held in thehousing to compress the canister.
 9. An inhaler according to any one ofthe preceding claims, wherein the canister engagement member is a leverrotatable about an axis parallel to the movement direction of the atleast one contact member.
 10. An inhaler according to any one of thepreceding claims, wherein the cam arrangement is arranged to hold the atleast one contact member in place at the end of its movement.
 11. Aninhaler according to any one of the preceding claims, wherein the ratioof the amount of driven movement of the loading member to the amount ofmovement of the at least one contact member being a non-linear functionof the position of the loading member.
 12. An inhaler for delivery byinhalation of a medicament from a canister which is compressible todeliver a dose of medicament, the inhaler comprising: a housing forholding a canister; a loading mechanism for loading a resilient loadingelement which is arranged, when loaded, to bias compression of thecanister, the loading mechanism comprising: a loading member engagingthe resilient loading element; and at least one contact member movablerelative to the housing to drive the loading member to load theresilient loading element, the ratio of the amount of driven movement ofthe loading member to the amount of movement of the at least one contactmember being a non-linear function of the position of the loadingmember.
 13. An inhaler according to claim 12, wherein said ratio reducesduring at least a major portion of the driven movement of the loadingmember.
 14. An inhaler according to claim 13, wherein said ratio isinversely proportional to the position of the loading member during saidmajor portion of its driven movement.
 15. An inhaler according to claim13 or 14, wherein said ratio varies with the position of the loadingmember during said major portion of the driven movement of the loadingmember such that the necessary force applied to the at least one contactmember is substantially constant.
 16. An inhaler according to any one ofclaims 12 to 15, wherein said ratio is reduced during an initial portionof the driven movement of the loading member relative to the subsequentportion.
 17. An inhaler according to any one of claims 12 to 16, whereinthe at least one contact member drives the loading member through anon-linear cam arrangement.
 18. An inhaler according to claim 17,wherein the cam arrangement is arranged to hold the at least one contactmember in place at the end of its movement.
 19. An inhaler according toclaim 17 or 18, the cam arrangement includes at least one cam surfaceprovided on the loading member and engaged by the at least one contactmember.
 20. An inhaler according to any one of claims 17 to 19, whereinthe loading member is driven to move in a direction orthogonal to saidmovement direction.
 21. An inhaler according to claim 20, wherein theloading member is driven to rotate in said direction orthogonal to saidmovement direction.
 22. An inhaler according to any one of claims 12 to21, having two contact members disposed on opposite sides of thehousing.
 23. An inhaler according to any one of claim 12 to 22, theresilient loading element biases a canister engagement member engageablewith a canister held in the housing to compress the canister.
 24. Aninhaler according to any one of the preceding claims, further comprisinga triggering mechanism arranged to hold the resilient loading elementagainst actuation of the canister and triggerable to release theresilient loading element.
 25. An inhaler according to claim 24, whereinthe triggering mechanism is arranged to be triggered by inhalation. 26.An inhaler constructed and arranged to operate substantially ashereinbefore described with reference to the accompanying drawings.